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ALICE Finds Most Light Nuclei Form via Decay-Then-Fusion in LHC Collisions

The result gives modelers a firmer basis for interpreting cosmic-ray antinuclei, including potential dark-matter signals.

Overview

  • Published in Nature, the analysis shows that nearly 90% of deuterons and antideuterons in proton–proton data arise from a short-lived delta resonance that decays before a nucleon fuses with neighbors.
  • Momentum correlations between pions and deuterons provide the key experimental signature linking the deuteron’s constituent to a delta-resonance decay.
  • The fusion step occurs slightly away from the collision point in a cooler region, which increases the chance that these fragile bound states survive.
  • The same mechanism is observed for nuclei and antinuclei, supplying a calibrated input for production models across matter and antimatter.
  • ALICE leaders call the finding a milestone based on LHC Run 2 proton-collision data that will recalibrate theoretical descriptions and guide next-generation astrophysical interpretations.